65 and we want to rv

How's your health?
You will most definitely need health insurance.

Get some quotes.
Start here and check other places
http://canamins.com/language/en/home/

Not sure about the rules, but I believe there's a limit to how long you can stay in the US. Plenty of Canadians on the site would be able to answer. If there is a limit, that would alter your "full-time" plans. You may find it necessary to keep an S&B home in Canada.

You will have lots of Canadian company! What do you want to do or see? How much do you want to spend (US)? These are questions you need to answer before choosing destinations. Do you want to be near a beach? If so, the costs are higher than if you just want a place out of the cold. Make reservations early! We moved each month. Monthly savings are significant. In some places, you may only reserve Februaryif you stay two or three months in one place. Most prefer the warmer climate roughly south of I4.

I take it you are eastern Canada Canadians.
Most boondocking opportunities in the states are out west.
But THIS LINK will be a good place to start looking for free or inexpensive campsites.
Although you are a little late you could look in the workkamping forum to see if there is an opportunity to exchange a little labor for a free or reduced rate campsite.

Look here: Snowbirds

Sorry, Florida is closed to Canadians. LOL
If it opens you might do a search on this Forum in the RV Parks section for Florida. Then search the results for `snowbird' to minimize the posts.